docs: def pad_event_roll(event_roll, length):
      """Pad event roll's length to given length
  
      Parameters
      ----------
      event_roll: np.ndarray, shape=(m,k)
          Event roll
  
      length : int
          Length to be padded
  
      Returns
      -------
      event_roll: np.ndarray, shape=(m,k)
          Padded event roll
  
      """
  
      if length > event_roll.shape[0]:
          padding = numpy.zeros((length-event_roll.shape[0], event_roll.shape[1]))
          event_roll = numpy.vstack((event_roll, padding))
  
      return event_roll